Condensed Consolidated Statements of Cash Flows (Unaudited) - Reconciliation of Cash, Cash Equivalents, and Restricted Cash - USD ($) $ in Millions	Mar. 31, 2019	Mar. 31, 2018
Current Assets:
Cash and cash equivalents	$ 1,910	$ 1,447
Restricted cash included in prepaid expenses and other	57	35
Noncurrent Assets:
Cash restricted for airport construction	1,018	0
Total cash, cash equivalents and restricted cash	$ 2,985	$ 1,482

Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant